1 files changed, 343 insertions, 0 deletions
diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
new file mode 100644
index 000000000..375a3bbe6
--- /dev/null
+++ b/net/core/sock_reuseport.c
@@ -0,0 +1,343 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * To speed up listener socket lookup, create an array to store all sockets
+ * listening on the same port.  This allows a decision to be made after finding
+ * the first socket.  An optional BPF program can also be configured for
+ * selecting the socket index from the array of available sockets.
+ */
+
+#include <net/sock_reuseport.h>
+#include <linux/bpf.h>
+#include <linux/idr.h>
+#include <linux/filter.h>
+#include <linux/rcupdate.h>
+
+#define INIT_SOCKS 128
+
+DEFINE_SPINLOCK(reuseport_lock);
+
+#define REUSEPORT_MIN_ID 1
+static DEFINE_IDA(reuseport_ida);
+
+int reuseport_get_id(struct sock_reuseport *reuse)
+{
+	int id;
+
+	if (reuse->reuseport_id)
+		return reuse->reuseport_id;
+
+	id = ida_simple_get(&reuseport_ida, REUSEPORT_MIN_ID, 0,
+			    /* Called under reuseport_lock */
+			    GFP_ATOMIC);
+	if (id < 0)
+		return id;
+
+	reuse->reuseport_id = id;
+
+	return reuse->reuseport_id;
+}
+
+static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
+{
+	unsigned int size = sizeof(struct sock_reuseport) +
+		      sizeof(struct sock *) * max_socks;
+	struct sock_reuseport *reuse = kzalloc(size, GFP_ATOMIC);
+
+	if (!reuse)
+		return NULL;
+
+	reuse->max_socks = max_socks;
+
+	RCU_INIT_POINTER(reuse->prog, NULL);
+	return reuse;
+}
+
+int reuseport_alloc(struct sock *sk, bool bind_inany)
+{
+	struct sock_reuseport *reuse;
+
+	/* bh lock used since this function call may precede hlist lock in
+	 * soft irq of receive path or setsockopt from process context
+	 */
+	spin_lock_bh(&reuseport_lock);
+
+	/* Allocation attempts can occur concurrently via the setsockopt path
+	 * and the bind/hash path.  Nothing to do when we lose the race.
+	 */
+	reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+					  lockdep_is_held(&reuseport_lock));
+	if (reuse) {
+		/* Only set reuse->bind_inany if the bind_inany is true.
+		 * Otherwise, it will overwrite the reuse->bind_inany
+		 * which was set by the bind/hash path.
+		 */
+		if (bind_inany)
+			reuse->bind_inany = bind_inany;
+		goto out;
+	}
+
+	reuse = __reuseport_alloc(INIT_SOCKS);
+	if (!reuse) {
+		spin_unlock_bh(&reuseport_lock);
+		return -ENOMEM;
+	}
+
+	reuse->socks[0] = sk;
+	reuse->num_socks = 1;
+	reuse->bind_inany = bind_inany;
+	rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
+
+out:
+	spin_unlock_bh(&reuseport_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL(reuseport_alloc);
+
+static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
+{
+	struct sock_reuseport *more_reuse;
+	u32 more_socks_size, i;
+
+	more_socks_size = reuse->max_socks * 2U;
+	if (more_socks_size > U16_MAX)
+		return NULL;
+
+	more_reuse = __reuseport_alloc(more_socks_size);
+	if (!more_reuse)
+		return NULL;
+
+	more_reuse->max_socks = more_socks_size;
+	more_reuse->num_socks = reuse->num_socks;
+	more_reuse->prog = reuse->prog;
+	more_reuse->reuseport_id = reuse->reuseport_id;
+	more_reuse->bind_inany = reuse->bind_inany;
+	more_reuse->has_conns = reuse->has_conns;
+
+	memcpy(more_reuse->socks, reuse->socks,
+	       reuse->num_socks * sizeof(struct sock *));
+	more_reuse->synq_overflow_ts = READ_ONCE(reuse->synq_overflow_ts);
+
+	for (i = 0; i < reuse->num_socks; ++i)
+		rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb,
+				   more_reuse);
+
+	/* Note: we use kfree_rcu here instead of reuseport_free_rcu so
+	 * that reuse and more_reuse can temporarily share a reference
+	 * to prog.
+	 */
+	kfree_rcu(reuse, rcu);
+	return more_reuse;
+}
+
+static void reuseport_free_rcu(struct rcu_head *head)
+{
+	struct sock_reuseport *reuse;
+
+	reuse = container_of(head, struct sock_reuseport, rcu);
+	sk_reuseport_prog_free(rcu_dereference_protected(reuse->prog, 1));
+	if (reuse->reuseport_id)
+		ida_simple_remove(&reuseport_ida, reuse->reuseport_id);
+	kfree(reuse);
+}
+
+/**
+ *  reuseport_add_sock - Add a socket to the reuseport group of another.
+ *  @sk:  New socket to add to the group.
+ *  @sk2: Socket belonging to the existing reuseport group.
+ *  May return ENOMEM and not add socket to group under memory pressure.
+ */
+int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
+{
+	struct sock_reuseport *old_reuse, *reuse;
+
+	if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
+		int err = reuseport_alloc(sk2, bind_inany);
+
+		if (err)
+			return err;
+	}
+
+	spin_lock_bh(&reuseport_lock);
+	reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
+					  lockdep_is_held(&reuseport_lock));
+	old_reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+					     lockdep_is_held(&reuseport_lock));
+	if (old_reuse && old_reuse->num_socks != 1) {
+		spin_unlock_bh(&reuseport_lock);
+		return -EBUSY;
+	}
+
+	if (reuse->num_socks == reuse->max_socks) {
+		reuse = reuseport_grow(reuse);
+		if (!reuse) {
+			spin_unlock_bh(&reuseport_lock);
+			return -ENOMEM;
+		}
+	}
+
+	reuse->socks[reuse->num_socks] = sk;
+	/* paired with smp_rmb() in reuseport_select_sock() */
+	smp_wmb();
+	reuse->num_socks++;
+	rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
+
+	spin_unlock_bh(&reuseport_lock);
+
+	if (old_reuse)
+		call_rcu(&old_reuse->rcu, reuseport_free_rcu);
+	return 0;
+}
+
+void reuseport_detach_sock(struct sock *sk)
+{
+	struct sock_reuseport *reuse;
+	int i;
+
+	spin_lock_bh(&reuseport_lock);
+	reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+					  lockdep_is_held(&reuseport_lock));
+
+	/* At least one of the sk in this reuseport group is added to
+	 * a bpf map.  Notify the bpf side.  The bpf map logic will
+	 * remove the sk if it is indeed added to a bpf map.
+	 */
+	if (reuse->reuseport_id)
+		bpf_sk_reuseport_detach(sk);
+
+	rcu_assign_pointer(sk->sk_reuseport_cb, NULL);
+
+	for (i = 0; i < reuse->num_socks; i++) {
+		if (reuse->socks[i] == sk) {
+			reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
+			reuse->num_socks--;
+			if (reuse->num_socks == 0)
+				call_rcu(&reuse->rcu, reuseport_free_rcu);
+			break;
+		}
+	}
+	spin_unlock_bh(&reuseport_lock);
+}
+EXPORT_SYMBOL(reuseport_detach_sock);
+
+static struct sock *run_bpf_filter(struct sock_reuseport *reuse, u16 socks,
+				   struct bpf_prog *prog, struct sk_buff *skb,
+				   int hdr_len)
+{
+	struct sk_buff *nskb = NULL;
+	u32 index;
+
+	if (skb_shared(skb)) {
+		nskb = skb_clone(skb, GFP_ATOMIC);
+		if (!nskb)
+			return NULL;
+		skb = nskb;
+	}
+
+	/* temporarily advance data past protocol header */
+	if (!pskb_pull(skb, hdr_len)) {
+		kfree_skb(nskb);
+		return NULL;
+	}
+	index = bpf_prog_run_save_cb(prog, skb);
+	__skb_push(skb, hdr_len);
+
+	consume_skb(nskb);
+
+	if (index >= socks)
+		return NULL;
+
+	return reuse->socks[index];
+}
+
+/**
+ *  reuseport_select_sock - Select a socket from an SO_REUSEPORT group.
+ *  @sk: First socket in the group.
+ *  @hash: When no BPF filter is available, use this hash to select.
+ *  @skb: skb to run through BPF filter.
+ *  @hdr_len: BPF filter expects skb data pointer at payload data.  If
+ *    the skb does not yet point at the payload, this parameter represents
+ *    how far the pointer needs to advance to reach the payload.
+ *  Returns a socket that should receive the packet (or NULL on error).
+ */
+struct sock *reuseport_select_sock(struct sock *sk,
+				   u32 hash,
+				   struct sk_buff *skb,
+				   int hdr_len)
+{
+	struct sock_reuseport *reuse;
+	struct bpf_prog *prog;
+	struct sock *sk2 = NULL;
+	u16 socks;
+
+	rcu_read_lock();
+	reuse = rcu_dereference(sk->sk_reuseport_cb);
+
+	/* if memory allocation failed or add call is not yet complete */
+	if (!reuse)
+		goto out;
+
+	prog = rcu_dereference(reuse->prog);
+	socks = READ_ONCE(reuse->num_socks);
+	if (likely(socks)) {
+		/* paired with smp_wmb() in reuseport_add_sock() */
+		smp_rmb();
+
+		if (!prog || !skb)
+			goto select_by_hash;
+
+		if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT)
+			sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, hash);
+		else
+			sk2 = run_bpf_filter(reuse, socks, prog, skb, hdr_len);
+
+select_by_hash:
+		/* no bpf or invalid bpf result: fall back to hash usage */
+		if (!sk2) {
+			int i, j;
+
+			i = j = reciprocal_scale(hash, socks);
+			while (reuse->socks[i]->sk_state == TCP_ESTABLISHED) {
+				i++;
+				if (i >= socks)
+					i = 0;
+				if (i == j)
+					goto out;
+			}
+			sk2 = reuse->socks[i];
+		}
+	}
+
+out:
+	rcu_read_unlock();
+	return sk2;
+}
+EXPORT_SYMBOL(reuseport_select_sock);
+
+int reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog)
+{
+	struct sock_reuseport *reuse;
+	struct bpf_prog *old_prog;
+
+	if (sk_unhashed(sk) && sk->sk_reuseport) {
+		int err = reuseport_alloc(sk, false);
+
+		if (err)
+			return err;
+	} else if (!rcu_access_pointer(sk->sk_reuseport_cb)) {
+		/* The socket wasn't bound with SO_REUSEPORT */
+		return -EINVAL;
+	}
+
+	spin_lock_bh(&reuseport_lock);
+	reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+					  lockdep_is_held(&reuseport_lock));
+	old_prog = rcu_dereference_protected(reuse->prog,
+					     lockdep_is_held(&reuseport_lock));
+	rcu_assign_pointer(reuse->prog, prog);
+	spin_unlock_bh(&reuseport_lock);
+
+	sk_reuseport_prog_free(old_prog);
+	return 0;
+}
+EXPORT_SYMBOL(reuseport_attach_prog);